Always watch out for the quiet ones. The maxim applies to rugby coaches as much as party-going teenagers. Mark McCall, Saracens' director of rugby, seldom volunteers a huge amount when encircled by microphones and notebooks but those who assume he has little to say are falling for sport's oldest trick. What coaches think and what they say in public are often barely related.

Even with Saracens seven points clear in the Premiership, people have been asking mostly about his Ravenhill reunion rather than posing the less obvious question: what sets him apart from the coaches in his wake? The answer cuts to the heart of the collegiate way Saracens operate.

First and foremost, according to the scrum-half Richard Wigglesworth, McCall's calm facade masks the cutest of tactical brains. "He's got an unbelievable knowledge of the game. You can mention any match we've been involved in at any stage in the last three years and he'll know exactly what happened and why." An ability to delegate is another key strength; the fact Sanderson and Gustard are encouraged to address the troops is no accident. "They are both talented speakers, so he lets them get up and talk," Wigglesworth says. "He's really good at letting people do what they're good at. Combined with his knowledge, it makes for a good team."

This unselfish attitude is entirely in character. As a player McCall was a hard-nut midfielder who made his presence felt in 13 Tests for Ireland without necessarily catching the eye. When he turned to coaching at Ulster it was only because the incumbent backs coach, Colin Wilkinson, was a car salesman who could not attend daytime training sessions.

McCall had to learn fast – and duly did so, helping Ulster win the 2006 Celtic league before arriving at Saracens in 2009 following a spell at Castres. "Mark has been unbelievable as director of rugby," says the club's England centre Brad Barritt. "One of the core traits at Saracens is humility and he has that in spades."

It is certainly hard to imagine many rival coaches tolerating the unique arrangement under which Dr Brendan Venter, McCall's predecessor, flies in once a month to monitor the club's wellbeing. It is not unlike Sir Alex Ferguson visiting the dressing room to check up on David Moyes. Venter – though based 6,000 miles away in South Africa he retains the title of technical director – remains a force of nature, "a whirlwind" to quote Wigglesworth. If McCall were remotely insecure he could easily be blown aside.

From the outside it is a fascinating dynamic, even though the pair were once team-mates at London Irish and Venter brought McCall to Saracens in the first place. "Some people from other clubs have said to me: 'That must be awful,'" McCall says. "Actually, it's the opposite.

"With Brendan's personality there was always the danger he'd interfere but he's been magnificent. He's a great barometer for me. Sometimes when you're in the middle of everything you need someone to tell you if the atmosphere within the playing group is right. He really cares about the club."

Doing things differently is all part of the Saracens mindset. Last September a group of the club's coaches visited Bayern Munich to study their methods. McCall believes it was a highly valuable exercise. "Their big thing, when they came back, was how connected with the club the staff were. They talked about the club being their skin. I look back six years to when I first arrived at Saracens and our chairman, Nigel Wray, was the only one who felt that way. I think we're now stacked with people like that. That's what you want. You want people who give a shit."

Last week's bonding trip to New York was merely the most recent illustration of this feelgood ethos but McCall is no laissez-faire tourist.

Less publicised were the fact-finding coaching visits to the New York Rangers ice hockey team and the New York Jets gridiron setup. The players relished the change of scenery but McCall rarely takes his eyes off the bigger picture. He has a law degree and also played cricket for Irish schools; his late father Conn played cricket for Ireland and was the president of the Irish Cricket Union.

He does not possess a one-dimensional sporting brain. As Barritt confirms: "With rugby you can often have too much information. The ability to select certain points is key and the method of delivery under Mark is impeccable. He is second to none in terms of the fine detail he puts in."

The time he spent playing at London Irish in the mid-90s was clearly instructive; no fewer than four of the back line he played in – Conor O'Shea, David Humphreys, Venter and himself – have become directors of rugby – "We talked a lot about rugby when we could get a word in edgeways" – while the wing Justin Bishop is also coaching and the scrum-half Niall Hogan is a surgeon.

Now fate decrees McCall and his old friend Humphreys must pit their wits against each other on the big stage, with Ulster hosting their first European quarter-final in Belfast since 1998-99, the season they won the competition.

McCall was officially their captain but suffered a neck injury early in the season and was mostly a spectator. While he famously helped Humphreys lift the trophy on Ulster's day of days, he has no plans to ease the massive weight of expectation swirling around Belfast: "Our job is to turn that expectation into something different: a burden, pressure, stress. We think we're as ready as we've ever been to attack this part of the season. We're in a very good place emotionally, mentally and physically."

Can Saracens stand up to the Ulstermen? Those writing off the English are, once again, underestimating the quiet achiever from Bangor.